Semiconductor device and method of manufacturing the same

ABSTRACT

A ferroelectric capacitor is formed above a semiconductor substrate ( 1 ), and thereafter, wirings ( 24   a ) are formed. A barrier film ( 25 ) covering the wirings ( 24   a ) is formed. A silicon oxide film ( 26 ) embedding gaps between the adjacent wirings ( 24   a ) is formed. The silicon oxide film ( 26 ) is polished until a surface of the barrier film ( 25 ) is exposed by a CMP method. A barrier film ( 27 ) is formed on the barrier film ( 25 ) and the silicon oxide film ( 26 ). Aluminum oxide films are formed as the barrier films ( 25, 27 ).

TECHNICAL FIELD

The embodiments discussed herein are directed to a semiconductor deviceincluding a ferroelectric capacitor and suitable for a nonvolatilememory, and a manufacturing method thereof.

BACKGROUND ART

In recent years, a development of a ferroelectric memory (FeRAM) holdinginformation on a ferroelectric capacitor by using a polarizationinversion of a ferroelectric substance is in progress. The ferroelectricmemory is a nonvolatile memory, in which the held information is notlost even if power supply is shut off, and it attracts attention inparticular because it is possible to realize a high integration, ahigh-speed driving, a high durability and a low power consumption.

As a ferroelectric film constituting the ferroelectric capacitor,ferroelectric oxide films having a perovskite crystal structure such asa PZT (Pb(Zr, Ti)O₃) film and an SBT (SrBi₂Ta₂O₉) film, whose amount ofremanent polarization are large, are mainly used. The amount of remanentpolarization of the PZT film is approximately 10 μC/cm² to 30 μC/cm².However, properties of the ferroelectric film (the amount of remanentpolarization, a dielectric constant, and so on) are easy to deteriorateby moisture. In the ferroelectric memory, a silicon oxide film or thelike having a high affinity with moisture is used as interlayerinsulating films. Besides, in a manufacturing process of theferroelectric memory, a heat treatment is performed for interlayerinsulating films and metal wirings. The moisture penetrating fromoutside and existing in the interlayer insulating films is decomposed tohydrogen and oxygen at the time of the heat treatment, and hydrogenreacts with oxygen atoms in the ferroelectric film. As a result of this,oxygen deficiency occurs in the ferroelectric film, crystallinity islowered and the properties deteriorate. Besides, the similar phenomenonmay occur by using the ferroelectric memory for a long time.

The deterioration of properties in accordance with the penetration ofmoisture and the diffusion of hydrogen as stated above may occur notonly in the ferroelectric capacitor but also in other elements such as atransistor in a semiconductor device.

An aluminum oxide film is therefore formed conventionally above theferroelectric capacitor with a view to prevent the penetration ofmoisture and the diffusion of hydrogen, and so on. For example, there isan art in which the aluminum oxide film is formed to directly wrap theferroelectric capacitor. Besides, there also is an art in which thealuminum oxide film is formed at further upward of a wiring layerpositioning above the ferroelectric capacitor. Those arts are describedin, for example, Patent Documents 1 to 5.

However, it cannot be said that the ferroelectric properties are enoughsecured by the above-stated conventional arts.

Patent Document 1: Japanese Patent Application Laid-open No. 2003-197878

Patent Document 2: Japanese Patent Application Laid-open No. 2001-68639

Patent Document 3: Japanese Patent Application Laid-open No. 2003-174145

Patent Document 4: Japanese Patent Application Laid-open No. 2002-176149

Patent Document 5: Japanese Patent Application Laid-open No. 2003-100994

SUMMARY OF THE INVENTION

It is an aspect of the embodiments discussed herein to provide asemiconductor device, including: a ferroelectric capacitor above asemiconductor substrate, and including a bottom electrode, aferroelectric film and a top electrode; a first wiring above theferroelectric capacitor, a part of the first wiring being connected toone of the top electrode and bottom electrode; a barrier layer directlycovering the first wiring, and preventing diffusion of hydrogen ormoisture, a surface of the barrier layer being flat; an interlayerinsulating film on the barrier layer; and a second wiring on theinterlayer insulating film, a part of the second wiring being connectedto the first wiring.

These together with other aspects and advantages which will besubsequently apparent, reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a structure of a ferroelectric memory(semiconductor device) according to a reference example;

FIG. 2A is a plan view showing a ferroelectric memory according to afirst embodiment;

FIG. 2B is a sectional view showing the ferroelectric memory accordingto the first embodiment;

FIG. 3A is a sectional view showing a manufacturing method of theferroelectric memory according to the first embodiment;

FIG. 3B is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3A;

FIG. 3C is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3B;

FIG. 3D is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3C;

FIG. 3E is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3D;

FIG. 3F is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3E;

FIG. 3G is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3F;

FIG. 3H is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3G;

FIG. 3I is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3H;

FIG. 3J is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3I;

FIG. 3K is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3J;

FIG. 3L is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3K;

FIG. 3M is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3L;

FIG. 3N is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3M;

FIG. 3O is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3N;

FIG. 3P is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3O;

FIG. 3Q is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3P;

FIG. 3R is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3Q;

FIG. 3S is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3R;

FIG. 3T is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3S;

FIG. 3U is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3T;

FIG. 3V is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3U;

FIG. 3W is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3V;

FIG. 3X is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3W;

FIG. 3Y is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3X;

FIG. 4 is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 3Q as same as FIG. 3R;

FIG. 5A is a view showing a leaving path of moisture in the firstembodiment;

FIG. 5B is a view showing a leaving path of moisture in the referenceexample;

FIG. 6A is a sectional view showing a manufacturing method of aferroelectric memory according to a second embodiment;

FIG. 6B is a sectional view showing the manufacturing method of theferroelectric memory following to FIG. 6A;

FIG. 7 is a sectional view showing the ferroelectric memory according tothe second embodiment;

FIG. 8 is a sectional view showing a ferroelectric memory according to athird embodiment; and

FIG. 9 is a sectional view showing a ferroelectric memory according to afourth embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments are concretely described with reference to theattached drawings.

REFERENCE EXAMPLE

First, a reference example is described. This reference example is anart in which the present inventors came to an idea during a processreaching the present embodiment. FIG. 1 is a sectional view showing astructure of a ferroelectric memory (semiconductor device) according tothe reference example.

As shown in FIG. 1, an element isolation region 1012 defining elementregions is formed on a semiconductor substrate 1010 such as a siliconsubstrate. Wells 1014 a and 1014 b are formed in the element regionsdefined by the element isolation region 1012.

Gate electrodes (gate wirings) 1018 are formed on the wells 1014 a and1014 b via gate insulating films 1016. The gate electrode 1018 has apolycide structure in which, for example, a metal silicide film such asa tungsten silicide film is formed on a poly-silicon film. An insulatingfilm 1019 such as a silicon oxide film is formed on the gate electrode1018. A sidewall insulating film 1020 is formed at lateral sides of thegate electrode 1018 and the insulating film 1019.

Source/drain diffusion layers 1022 are formed at surfaces of the wells1014 a and 1014 b so as to sandwich the gate electrode 1018 in a planview. Thus, transistors 1024 each having the gate electrode 1018 and thesource/drain diffusion layers 1022 are constituted. A gate length of thetransistor 1024 is, for example, 0.35 μm, or 0.11 μm to 0.18 μm.

Further, a SiON film 1025 and a silicon oxide film 1026 covering thetransistors 1024 are sequentially formed. A thickness of the SiON film1025 is, for example, 200 nm, and a thickness of the silicon oxide film1026 is, for example, 600 nm. An interlayer insulating film 1027 iscomposed of the SiON film 1025 and the silicon oxide film 1026. Asurface of the interlayer insulating film 1027 is flattened.

A silicon oxide film 1034 of which film thickness is, for example, 100nm is formed on the interlayer insulating film 1027. The silicon oxidefilm 1034 is also flat because it is formed on the flattened interlayerinsulating film 1027.

A bottom electrode 1036 is formed on the silicon oxide film 1034. Thebottom electrode 1036 is composed of, for example, an aluminum oxidefilm 1036 a of which film thickness is 20 nm to 50 nm and a Pt film 1036b of which film thickness is 100 nm to 200 nm formed thereon.

A ferroelectric film 1038 is formed on the bottom electrode 1036. As theferroelectric film 1038, a PbZr_(1-X)Ti_(X)O₃ film (PZT film) of whichfilm thickness is, for example, 100 nm to 250 nm is used.

A top electrode 1040 is formed on the ferroelectric film 1038. The topelectrode 1040 is composed of, for example, an IrO_(X) film 1040 a ofwhich film thickness is 25 nm to 75 nm and an IrO_(Y) film 1040 b ofwhich film thickness is 150 nm to 250 nm formed thereon. Incidentally, acomposition ratio Y of oxygen of the IrO_(Y) film 1040 b is set to behigher than a composition ratio X of the oxygen of the IrO_(X) film 1040a.

A ferroelectric capacitor 1042 is composed of the bottom electrode 1036,the ferroelectric film 1038 and the top electrode 1040.

A barrier film 1044 is formed so as to cover an upper surface and sidesurfaces of the ferroelectric film 1038 and the top electrode 1040. Asthe barrier film 1044, an aluminum oxide (Al₂O₃) film of which thicknessis, for example, 20 nm to 100 nm is used.

The barrier film 1044 is a film having a function preventing diffusionof hydrogen and moisture. If hydrogen or moisture reaches theferroelectric film 1038, a metal oxide constituting the ferroelectricfilm 1038 is reduced by the hydrogen or moisture, and an electricproperty of the ferroelectric capacitor 1042 deteriorates. With thebarrier film 1044 being formed to cover the upper surface and sidesurfaces of the ferroelectric film 1038 and the top electrode 1040, itis possible to suppress the deterioration of the electric property ofthe ferroelectric capacitor 1042 because it is suppressed that hydrogenand moisture reach the ferroelectric film 1038.

Further, a barrier film 1046 covering the barrier film 1044 and theferroelectric capacitor 1042 is formed. For example, an aluminum oxidefilm of which film thickness is 20 nm to 100 nm is used as the barrierfilm 1046. The barrier film 1046 is a film having a function preventingthe diffusion of hydrogen and moisture as same as the barrier film 1044.

An interlayer insulating film 1048 such as a silicon oxide film of whichfilm thickness is, for example, 1500 nm is formed on the barrier film1046. A surface of the interlayer insulating film 1048 is flattened.

Contact holes 1050 a and 1050 b reaching the source/drain diffusionlayer 1022 are formed in the interlayer insulating film 1048, thebarrier film 1046, the silicon oxide film 1034 and the interlayerinsulating film 1027. Besides, a contact hole 1052 a reaching the topelectrode 1040 is formed in the interlayer insulating film 1048, thebarrier film 1046 and the barrier film 1044. Further, a contact hole1052 b reaching the bottom electrode 1036 is formed in the interlayerinsulating film 1048, the barrier film 1046 and the barrier film 1044.

Barrier metal films (not shown) are formed inside the contact holes 1050a and 1050 b. The barrier metal film is composed of, for example, a Tifilm of which film thickness is 20 nm and a TiN film of which filmthickness is 50 nm formed thereon. Within the barrier metal film, the Tifilm is formed to reduce a contact resistance, and the TiN film isformed to prevent the diffusion of tungsten of a conductive plugmaterial. Barrier metal films formed in each of later-described contactholes are formed for similar purposes.

Further, conductive plugs 1054 a and 1054 b composed of tungsten arerespectively embedded inside the contact holes 1050 a and 1050 b, inwhich the barrier metal films are formed.

A wiring 1056 a electrically connected to the conductive plug 1054 a andthe top electrode 1040 is formed on the interlayer insulating film 1048and inside the contact hole 1052 a. Besides, a wiring 1056 belectrically connected to the bottom electrode 1036 is formed on theinterlayer insulating film 1048 and inside the contact hole 1052 b.Further, a wiring 1056 c electrically connected to the conductive plug1054 b is formed on the interlayer insulating film 1048. The wirings1056 a, 1056 b and 1056 c (a first metal wiring layer 1056) are composedof, for example, a TiN film of which film thickness is 150 nm, an AlCualloy film of which film thickness is 550 nm formed thereon, a Ti filmof which film thickness is 5 nm formed thereon and a TiN film of whichfilm thickness is 150 nm formed thereon.

Thus, the source/drain diffusion layer 1022 of the transistor 1024 andthe top electrode 1040 of the ferroelectric capacitor 1042 areelectrically connected via the conductive plug 1054 a and the wiring1056 a, and a 1T1C-type memory cell of FeRAM having one transistor 1024and one ferroelectric capacitor 1042 is constituted. Plural memory cellsare arranged in a memory cell region of an FeRAM chip though they arenot shown.

Further, a barrier film 1058 covering upper surfaces and side surfacesof the wirings 1056 a, 1056 b and 1056 c is formed. An aluminum oxidefilm of which film thickness is, for example, 20 nm is used as thebarrier film 1058.

The barrier film 1058 is a film having a function preventing thediffusion of hydrogen and moisture as same as the barrier films 1044 and1046. Besides, the barrier film 1058 is also used to suppress damage byplasma.

A silicon oxide film 1060 of which film thickness is, for example, 2600nm is formed on the barrier film 1058. A surface of the silicon oxidefilm 1060 is flattened. A thickness of the silicon oxide film 1060 onthe wirings 1056 a, 1056 b and 1056 c is, for example, 1000 nm.

A silicon oxide film 1061 of which film thickness is, for example, 100nm is formed on the silicon oxide film 1060. The silicon oxide film 1061is also flat because it is formed on the flattened silicon oxide film1060.

A barrier film 1062 is formed on the silicon oxide film 1061. Analuminum oxide film of which film thickness is, for example, 20 nm to 70nm is used as the barrier film 1062. The barrier film 1062 is also flatbecause it is formed on the flat silicon oxide film 1061.

The barrier film 1062 is a film having a function to prevent thediffusion of hydrogen and moisture as same as the barrier films 1044,1046 and 1058. Further, the barrier film 1062 is flat, and therefore, itis formed with extremely good coverage (covering property) compared tothe barrier films 1044, 1046 and 1058. Consequently, it is possible toprevent the diffusion of hydrogen and moisture more surely.Incidentally, the barrier film 1062 is formed not only on the memorycell region of the FeRAM chip where plural memory cells having theferroelectric capacitors 1042 are arranged, but also for a whole surfaceof the FeRAM chip including a peripheral circuit region and so on.

A silicon oxide film 1064 of which film thickness is, for example, 50 nmto 100 nm is formed on the barrier film 1062.

An interlayer insulating film 1066 is composed of the barrier film 1058,the silicon oxide film 1060, the silicon oxide film 1061, the barrierfilm 1062 and the silicon oxide film 1064.

A contact hole 1068 reaching the wiring 1056 c is formed in theinterlayer insulating film 1066.

A barrier metal film (not shown) is formed inside the contact hole 1068.The barrier metal film is composed of, for example, a Ti film of whichfilm thickness is 20 nm and a TiN film of which film thickness is 50 nmformed thereon. Incidentally, the barrier metal film may be composed ofonly the TiN film without the Ti film.

A conductive plug 1070 composed of tungsten is embedded inside thecontact hole 1068, in which the barrier metal film is formed.

A wiring 1072 a is formed on the interlayer insulating film 1066.Besides, a wiring 1072 b electrically connected to the conductive plug1070 is formed on the interlayer insulating film 1066. The wirings 1072a and 1072 b (a second metal wiring layer 1072) are composed of, forexample, a TiN film of which film thickness is 50 nm, an AlCu alloy filmof which film thickness is 500 nm formed thereon, a Ti film of whichfilm thickness is 5 nm formed thereon and a TiN film of which filmthickness is 150 nm formed thereon.

Further, a silicon oxide film 1074 covering the wirings 1072 a and 1072b is formed. A thickness of the silicon oxide film 1074 is, for example,2200 nm. A surface of the silicon oxide film 1074 is flattened.

A silicon oxide film 1076 of which film thickness is, for example, 100nm is formed on the silicon oxide film 1074. The silicon oxide film 1076is also flat because it is formed on the flattened silicon oxide film1074.

A barrier film 1078 is formed on the silicon oxide film 1076. Analuminum oxide film of which film thickness is, for example, 20 nm to100 nm is used as the barrier film 1078. The barrier film 1078 is alsoflat because it is formed on the flat silicon oxide film 1076.

The barrier film 1078 is a film having a function preventing thediffusion of hydrogen and moisture as same as the barrier films 1044,1046, 1058 and 1062. Further, the barrier film 1078 is flat, andtherefore, it is formed with an extremely good coverage (coveringproperty) as same as the barrier film 1062 compared to the barrier films1044, 1046 and 1058. Consequently, it is possible to prevent thediffusion of hydrogen and moisture more surely. Incidentally, thebarrier film 1078 is formed not only on the memory cell region of theFeRAM chip where plural memory cells having the ferroelectric capacitors1042 are arranged, but also for a whole surface of the FeRAM chipincluding a peripheral circuit region and so on.

A silicon oxide film 1080 of which film thickness is, for example, 100nm is formed on the barrier film 1078.

An interlayer insulating film 1082 is composed of the silicon oxide film1074, the silicon oxide film 1076, the barrier film 1078 and the siliconoxide film 1080.

Contact holes 1084 a and 1084 b respectively reaching the wirings 1072 aand 1072 b are formed in the interlayer insulating film 1082.

Barrier metal films (not shown) are formed inside the contact holes 1084a and 1084 b. The barrier metal film is composed of by, for example, aTi film of which film thickness is 20 nm and a TiN film of which filmthickness is 50 nm formed thereon. Incidentally, the barrier metal filmmay be composed of only the TiN film without the Ti film.

Conductive plugs 1086 a and 1086 b composed of tungsten are respectivelyembedded inside the contact holes 1084 a and 1084 b, in which thebarrier metal films are formed.

A wiring 1088 a electrically connected to the conductive plug 1086 a anda wiring (bonding pad) 1088 b electrically connected to the conductiveplug 1086 b are formed on the interlayer insulating film 1082. Thewirings 1088 a and 1088 b (a third metal wiring layer 1088) are composedof, for example, a TiN film of which film thickness is 50 nm, an AlCualloy film of which film thickness is 500 nm formed thereon and a TiNfilm of which film thickness is 150 nm formed thereon.

Further, a silicon oxide film 1090 covering the wirings 1088 a and 1088b is formed. A thickness of the silicon oxide film 1090 is, for example,100 nm to 300 nm. A silicon nitride film 1092 of which film thicknessis, for example, 350 nm is formed on the silicon oxide film 1090. Apolyimide resin film 1094 of which film thickness is, for example, 2 μmto 6 μm is formed on the silicon nitride film 1092.

An opening 1096 reaching the wiring (bonding pad) 1088 b is formed inthe polyimide resin film 1094, the silicon nitride film 1092 and thesilicon oxide film 1090. In other words, an opening 1096 a reaching thewiring (bonding pad) 1088 b is formed in the silicon nitride film 1092and the silicon oxide film 1090. Further, an opening 1096 b is formed inthe polyimide resin film 1094 at a region including the opening 1096 a.

An external circuit (not-shown) is electrically connected to the wiring(bonding pad) 1088 b via the opening 1096.

Thus, the semiconductor device according to the reference example isconstituted.

In the semiconductor device as described above, the barrier films 1062and 1078, which are flat and have good coverage (covering property), areformed in addition to the barrier films 1044, 1046 and 1058, andtherefore, it is possible to interrupt hydrogen and moisture, and toprevent that hydrogen and moisture reach the ferroelectric film 1038more surely. Namely, even if defects occur at both of the barrier films1062 and 1078, it is possible to prevent the penetration of hydrogen andmoisture by at least one of the barrier films because defected positionsmay be displaced from one another in most cases.

However, it turned out that there is a case when defect may occur in thebarrier metal film and the tungsten film when the conductive plugs 1070,1086 a and 1086 b are formed, in the reference example as describedabove. A factor of the above was studied, and it was found that themoisture left from the silicon oxide films 1060, 1061, 1074 and 1076under the barrier film 1062 or 1078 remains while adhering on sidewallsof the contact holes 1068, 1084 a and 1084 b, at the time of ahigh-temperature process at approximately 400° C. performed when thebarrier metal film and the tungsten film are formed.

It is preferable that NSG (Non-Silicate-Glass) films formed by a plasmaCVD method in which source gas is TEOS (Tetra-Ethyl-Ortho-Silicate) areused for the silicon oxide films 1060, 1061, 1074 and 1076, but moistureremains within the films. The moisture is leaving from inside the filmsat the time of the high-temperature process after that. However, in theabove-described reference example, the barrier film 1062 or 1078 existsover the silicon oxide film 1060, 1061, 1074 or 1076, and therefore, themoisture cannot get out to upward. Accordingly, the moisture gathers tothe sidewall of the contact hole 1068, 1084 a or 1084 b so as to get outof the films. As a result, the moisture, which reaches the sidewalls butis unable to completely leave toward outside, remains at the sidewallsof the contact holes or inside thereof. Accordingly, growths of thebarrier metal film and the tungsten film are disturbed.

The present inventors therefore studied further more, and came toembodiments as stated below.

First Embodiment

Here, a first embodiment is described. FIG. 2A is a plan view showing aferroelectric memory (semiconductor device) according to the firstembodiment, and FIG. 2B is a sectional view similarly showing theferroelectric memory.

As shown in FIG. 2A and FIG. 2B, the ferroelectric memory according tothe first embodiment may be defined into a memory cell portion 101, alogic circuit portion 102, a peripheral circuit portion 103 and a padportion 104. In FIG. 2A and FIG. 2B, these portions are arranged in onedirection, but it is not necessary that these portions are arranged inone direction, and more elements and so on are provided at respectiveportions.

In the present embodiment, element isolation regions 2 defining elementregions are formed on a semiconductor substrate 1 such as a siliconsubstrate. Wells 1 a are formed in the element regions defined by theelement isolation regions 2. A conductive type of the well 1 a can beselected arbitrary in accordance with an element to be formed thereon.

Gate electrodes (gate wirings) 4 are formed on the wells 1 a via gateinsulating films 3. The gate electrode 4 has a polycide structure inwhich, for example, a metal silicide film such as a tungsten silicidefilm is formed on a poly-silicon film. A cap insulating film 5 such as asilicon oxide film is formed on the gate electrode 4. A sidewallinsulating film 6 is formed at lateral sides of the gate electrode 4 andthe cap insulating film 5.

Source/drain diffusion layers having an LDD structure are formed atsurfaces of the wells 1 a so as to sandwich the gate electrodes 4 in aplan view. A low-concentration diffusion layer 7 and ahigh-concentration diffusion layer 8 are provided to the source/draindiffusion layer. Thus, a transistor having the gate electrode 4 and thesource/drain diffusion layers having the LDD structure is constituted.When the transistor is an N-channel MOS transistor, boron (B) isintroduced to the well 1 a, phosphorus (P) is introduced to thelow-concentration diffusion layer 7, and arsenic (As) is introduced tothe high-concentration diffusion layer 8.

Further, a SiON film 9 and a silicon oxide film 10 covering thetransistor are sequentially formed. A surface of the silicon oxide film10 is flattened. A silicon oxide film 11 and a barrier film 12 aresequentially formed on the silicon oxide film 10.

Bottom electrodes 13 a are formed on the barrier film 12. Aferroelectric film 14 a is formed on each of the bottom electrodes 13 a.Further, a top electrode 15 a is formed on each of the ferroelectricfilms 14 a. A ferroelectric capacitor is composed of the bottomelectrode 13 a, the ferroelectric film 14 a and the top electrode 15 a.

A barrier film 16 is formed so as to cover an upper surface and sidesurfaces of the ferroelectric film 14 a and the top electrode 15 a. Thebarrier film 16 is a film having a function preventing diffusion ofhydrogen and moisture. If hydrogen or moisture reaches the ferroelectricfilm 14 a, a metal oxide composing the ferroelectric film 14 a isreduced by the hydrogen or moisture, and an electric property of theferroelectric capacitor deteriorates. With the barrier film 16 beingformed so as to cover the upper surface and side surfaces of theferroelectric film 14 a and the top electrode 15 a, it is possible tosuppress the deterioration of the electric property of the ferroelectriccapacitor because hydrogen and moisture are suppressed to reach theferroelectric film 14 a.

Further, a barrier film 17 covering the barrier film 16 and theferroelectric capacitor is formed. The barrier film 17 is a film havingthe function to prevent the diffusion of hydrogen and moisture as sameas the barrier film 16.

An interlayer insulating film 18 such as a silicon oxide film is formedon the barrier film 17. A surface of the interlayer insulating film 18is flattened.

Contact holes 20 reaching the high-concentration diffusion layers 8 ofthe source/drain diffusion layers are formed in the interlayerinsulating film 18, the barrier film 17, the barrier film 12, thesilicon oxide film 11, the silicon oxide film 10 and the SiON film 9.Besides, contact holes 23 t reaching the top electrodes 15 a are formedin the interlayer insulating film 18, the barrier film 17 and thebarrier film 16. Further, contact holes 23 b reaching the bottomelectrodes 13 a are formed in the interlayer insulating film 18, thebarrier film 17 and the barrier film 16.

Barrier metal films (not-shown) are formed inside the contact holes 23 tand 23 b. The barrier metal film is composed of, for example, a Ti filmand a TiN film formed thereon. The Ti film is formed to reduce a contactresistance, and the TiN film is formed to prevent diffusion of tungstenof a conductive plug material within the barrier metal film. Barriermetal films formed in each of later-described contact holes are formedfor similar purposes.

Further, conductive plugs 21 composed of tungsten are embedded insidethe contact holes 23 t and 23 b, in which the barrier metal films areformed.

Wirings 24 a (first wirings) are formed on the interlayer insulatingfilm 18, and inside the contact holes 23 t and 23 b. One of the wirings24 a electrically connects the conductive plug 21 connected to thehigh-concentration diffusion layer 8 and the top electrode 15 a.

Thus, the high-concentration diffusion layer 8 of the transistor and thetop electrode 15 a of the ferroelectric capacitor are electricallyconnected via the one of the wirings 24 a, and a 1T1C-type memory cellof FeRAM having one transistor and one ferroelectric capacitor isconstituted. Incidentally, plural memory cells are arranged in a memorycell region of an FeRAM chip though they are not shown.

Further, a barrier film 25 covering upper surfaces and side surfaces ofthe wirings 24 a is formed. The barrier film 25 is formed to follow thewirings 24 a, and therefore, concave and convex exist around the wirings24 a. In the present embodiment, a silicon oxide film 26 is formed so asto embed these concave and convex. Surfaces of the barrier film 25 andthe silicon oxide film 26 are flattened.

A barrier film 27 is formed on the barrier film 25 and the silicon oxidefilm 26. Since the barrier film 25 and the silicon oxide film 26 areflattened, the barrier film 27 is also flat. Silicon oxide films 28 and29 are sequentially formed on the barrier film 27. A surface of thesilicon oxide film 29 is flattened. A barrier layer is composed of thebarrier films 25 and 27. Besides, an interlayer insulating film iscomposed of the silicon oxide films 28 and 29.

Contact holes 30 reaching a part of the wirings 24 a are formed in thesilicon oxide film 29, the silicon oxide film 28, the barrier film 27and the barrier film 25. Barrier metal films (not shown) are formedinside the contact holes 30. The barrier metal film is composed of, forexample, a Ti film and a TiN film formed thereon. Incidentally, thebarrier metal film may be composed of only the TiN film without the Tifilm.

A conductive plug 31 composed of tungsten is embedded inside the contacthole 30 in which the barrier metal film is formed.

Wirings 32 a (second wirings) in which a part thereof is connected tothe conductive plugs 31 are formed on the silicon oxide film 28.Further, a silicon oxide film 33 covering the wirings 32 a is formed. Asurface of the silicon oxide film 33 is flattened. A silicon oxide film34 is formed on the silicon oxide film 33. The silicon oxide film 34 isalso flat because it is formed on the flattened silicon oxide film 33.

Contact holes 35 reaching ones of the wirings 32 a are formed in thesilicon oxide films 34 and 33. The barrier metal films (not shown) areformed inside the contact holes 35. The barrier metal film is composedof, for example, a Ti film and a TiN film formed thereon. Incidentally,the barrier metal film may be composed of only the TiN film without theTi film.

A conductive plug 36 composed of tungsten is embedded inside the contacthole 35, in which the barrier metal film is formed.

Wirings 37 electrically connected to the conductive plugs 36 are formedon the silicon oxide film 34.

Further, a silicon oxide film 38 covering the wirings 37 is formed. Asilicon nitride film 39 is formed on the silicon oxide film 38. Anopening 40 exposing a part of the wiring 37 in the pad portion 104 isformed in the silicon oxide film 38 and the silicon nitride film 39. Theportion of the wiring 37 exposed from the opening 40 functions as abonding pad.

A polyimide resin film 41 is formed on the silicon nitride film 39. Anopening 42 matching with the opening 40 in the pad portion 104 is formedin the polyimide resin film 41.

An external circuit (not-shown) is electrically connected to the portionfunctioning as the bonding pad of the wiring 37 via the openings 42 and40.

Incidentally, some of the wirings and the contact holes are formed in aring shape in the pad portion 104, and the portion functions as amoisture-resistant ring 42.

Next, a manufacturing method of the semiconductor device according tothe first embodiment is described. FIG. 3A to FIG. 3Y are sectionalviews showing the manufacturing method of the ferroelectric memory(semiconductor device) according to the first embodiment in processsequence.

First, as shown in FIG. 3A, the element isolation regions 2 defining theelement regions are formed on the surface of the semiconductor substrate1 such as a silicon substrate. Next, the wells 1 a are formed in theelement regions defined by the element isolation regions 2. Next, thetransistor including the gate insulating film 3, the gate electrode 4,the cap insulating film 5, the sidewall insulating film 6, thelow-concentration diffusion layers 7 and the high-concentrationdiffusion layers 8 is formed on the well 1 a. At this time, a thicknessof the gate insulating film 3 is, for example, approximately 6 nm to 7nm. A structure of the gate electrode 4 is a polycide structure composedof, for example, a poly-silicon film of which thickness is approximately50 nm, and a metal silicide film such as a tungsten silicide film ofwhich thickness is approximately 150 nm formed thereon. As the capinsulating film 5, a silicon oxide film of which thickness is, forexample, approximately 45 nm is formed. Besides, a gate length is, forexample, approximately 360 nm.

After that, as shown in FIG. 3B, the SiON film 9 covering thetransistors is formed by, for example, a plasma CVD method. A thicknessof the SiON film 9 is, for example, approximately 200 nm. Subsequently,the silicon oxide film (NSG film) 10 is formed on the SiON film 9 by,for example, a plasma CVD method in which source gas is TEOS. Athickness of the silicon oxide film 10 is, for example, 600 nm. Next,the surface of the silicon oxide film 10 is flattened by polishing forapproximately 200 nm by, for example, a CMP method.

Next, as shown in FIG. 3C, the silicon oxide film (NSG film) 11 isformed on the silicon oxide film 10 by, for example, a plasma CVD methodin which source gas is TEOS. A thickness of the silicon oxide film 11is, for example, 100 nm. After that, a heat treatment is performed forthe silicon oxide film 11 at 650° C. for 30 minutes, for example, undera nitrous oxide (N₂O) or nitrogen (N₂) atmosphere. As a result of this,a dehydration treatment of the silicon oxide film 11 is performed, and asurface of the silicon oxide film 11 is a little nitride. During theheat treatment, nitrogen is supplied with a flow rate of 20liter/minute, for example.

Subsequently, the barrier film 12 is formed on the silicon oxide film11. As the barrier film 12, an aluminum oxide film with a thickness of,for example, approximately 20 nm is formed by a PVD method. Next, a heattreatment (annealing) is performed by, for example, an RTA method at650° C. for 60 seconds. During the heat treatment, oxygen is suppliedwith the flow rate of 2 liter/minute, for example.

Next, as shown in FIG. 3D, a bottom electrode film 13 is formed on thebarrier film 12. As the bottom electrode film 13, a Pt film with athickness of, for example, approximately 155 nm is formed by a PVDmethod. After that, a ferroelectric film 14 is formed on the bottomelectrode film 13. As the ferroelectric film 14, a PZT film with athickness of, for example, approximately 150 nm to 200 nm is formed by aPVD method. Subsequently, a heat treatment (annealing) is performed by,for example, a RTA method at 585° C. for 90 seconds. During the heattreatment, oxygen is supplied with the flow rate of 0.025 liter/minute,for example.

Next, a top electrode film 15 is formed on the ferroelectric film 14.When the top electrode film 15 is formed, an IrO_(X) film is formed by,for example, a PVD method, and thereafter, an IrO_(Y) film is formed onthe IrO_(X) film by, for example, a PVD method. Thicknesses bf theIrO_(X) film and the IrO_(Y) film are, for example, approximately 50 nmand approximately 200 nm respectively. Note that, a heat treatment(annealing) is performed by, for example, a RTA method at 725° C. for 20seconds, between the formation of the IrO_(X) film and the formation ofthe IrO_(Y) film. During the heat treatment, oxygen is supplied with theflow rate of 0.025 liter/minute, for example.

Next, as shown in FIG. 3E, the top electrode film 15 is patterned with aresist pattern (not shown), and thereby, the top electrodes 15 a areformed. After that, recovery annealing is performed for theferroelectric film 14 at 650° C. for 60 minutes. During the recoveryannealing, oxygen is supplied to a vertical furnace with the flow rateof 20 liter/minute, for example.

Subsequently, the ferroelectric film 14 is patterned with another resistpattern (not shown), and thereby, a capacitor insulating film is formed.In the present description, this capacitor insulating film isrepresented as the ferroelectric film 14 a. Next, recovery annealing isperformed for the ferroelectric film 14 a at 350° C. for 60 minutes.During the recovery annealing, oxygen is supplied to a vertical furnacewith the flow rate of 20 liter/minute, for example.

Next, as shown in FIG. 3F, the barrier film 16 covering the uppersurface and side surfaces of the top electrode 15 a and theferroelectric film 14 a is formed. As the barrier film 16, an aluminumoxide film with a thickness of, for example, approximately 50 nm isformed by a PVD method. After that, recovery annealing is performed at550° C. for 60 minutes in a vertical furnace, for example. During therecovery annealing, oxygen is supplied with the flow rate of 20liter/minute, for example.

Subsequently, as shown in FIG. 3G, the bottom electrode film 13 and thebarrier film 16 are patterned with still another resist pattern (notshown), and thereby the bottom electrodes 13 a are formed. Theferroelectric capacitor is composed of the bottom electrode 13 a, theferroelectric film 14 a and the top electrode 15 a. Next, recoveryannealing is performed at 650° C. for 60 minutes in a vertical furnace,for example. During the recovery annealing, oxygen is supplied with theflow rate of 20 liter/minute, for example. Next, the barrier film 17covering the ferroelectric capacitor and the barrier film 16 is formed.As the barrier film 17, an aluminum oxide film with a thickness of, forexample, approximately 20 nm is formed by a PVD method. After that,recovery annealing is performed at 550° C. for 60 minutes in a verticalfurnace, for example. During the recovery annealing, oxygen is suppliedwith the flow rate of 20 liter/minute, for example.

Subsequently, as shown in FIG. 3H, the interlayer insulating film 18completely covering the ferroelectric capacitor and the barrier film 17is formed. As the interlayer insulating film 18, a silicon oxide film(NSG film) is formed by, for example, a plasma CVD method in whichsource gas is TEOS. A thickness of the interlayer insulating film 18 is,for example, 1500 nm. Next, the surface of the interlayer insulatingfilm 18 is flattened by polishing by a CMP method, for example. Next,plasma annealing using an N₂O plasma is performed in a CVD apparatus,for example, and thereby, the surface of the interlayer insulating film18 is nitride. The plasma annealing is performed, at 350° C. for 2minutes for example.

After that, as shown in FIG. 3I, the interlayer insulating film 18, thebarrier film 17, the barrier film 12, the silicon oxide film 11, thesilicon oxide film 10 and the SiON film 9 are patterned with a resistmask 19 in which a predetermined pattern is formed, and thereby, thecontact holes 20 reaching the high-concentration diffusion layers 8 areformed.

Subsequently, the Ti film with a thickness of approximately 20 nm andthe TiN film with a thickness of approximately 50 nm are sequentiallyformed as the barrier metal film (not shown) by a PVD method, forexample, for the whole surface. Next, a tungsten film with a thicknessof approximately 500 nm is formed by a CVD method, for example, for thewhole surface. Next, the tungsten film, the TiN film and the Ti film arepolished by a CMP method, for example, until the interlayer insulatingfilm 18 is exposed. As a result of this, the tungsten film remains inthe contact hole 20, and the conductive plug 21 is composed of thetungsten film as shown in FIG. 3J. After that, plasma annealing usingN₂O plasma is performed in a CVD apparatus, for example, and thereby,the surface of the interlayer insulating film 18 is nitride. This plasmaannealing is performed at 350° C. for 2 minutes, for example.Subsequently, a SiON film 22 with a thickness of approximately 100 nm isformed on the interlayer insulating film 18 by a plasma CVD method, forexample.

Next, as shown in FIG. 3K, the SiON film 22, the interlayer insulatingfilm 18, the barrier film 17 and the barrier film 12 are patterned witha resist mask (not shown) in which a predetermined pattern is formed,and thereby, the contact holes 23 t reaching the top electrodes 15 a andthe contact holes 23 b reaching the bottom electrodes 13 a are formed.Next, recovery annealing is performed at 500° C. for 60 minutes in avertical furnace, for example. During the recovery annealing, oxygen issupplied with the flow rate of 20 liter/minute, for example.

After that, as shown in FIG. 3L, the SiON film 22 is removed by etching(etched back).

Subsequently, as shown in FIG. 3M, a conductive film 24 is formed by aPVD method, for example. When the conductive film 24 is formed, forexample, a TiN film with a thickness of 150 nm, an AlCu alloy film witha thickness of 550 nm, a Ti film with a thickness of 5 nm and the TiNfilm with a thickness of 150 nm are sequentially formed.

Next, as shown in FIG. 3N, the conductive film 24 is patterned with aresist mask (not shown) in which a predetermined pattern is formed, andthereby, the wirings 24 a are formed. Next, a heat treatment (annealing)is performed at 350° C. for 30 minutes in a vertical furnace, forexample. During the heat treatment, oxygen is supplied with the flowrate of 20 liter/minute, for example.

After that, as shown in FIG. 30, the barrier film 25 covering thewirings 24 a is formed. As the barrier film 25, an aluminum oxide filmwith a thickness of, for example, approximately 20 nm is formed by a PVDmethod.

Subsequently, as shown in FIG. 3P, the silicon oxide film 26 embeddinggaps between the adjacent wirings 24 a is formed. As the silicon oxidefilm 26, a NSG film is formed by a plasma CVD method in which source gasis TEOS, for example.

Next, as shown in FIG. 3Q, the silicon oxide film 26 is polished by aCMP method, for example, until a surface of the barrier film 25 isexposed. After that, plasma annealing is performed with N₂O plasma in aCVD apparatus, for example, and thereby, a surface of the silicon oxidefilm 26 is nitride. The plasma annealing is performed, for example, at350° C. for 4 minutes. In this plasma annealing, dehydration treatmentof the silicon oxide film 26 is also performed.

Next, as shown in FIG. 3R and FIG. 4, the barrier film 27 is formed onthe barrier film 25 and the silicon oxide film 26. As the barrier film27, an aluminum oxide film with a thickness of, for example,approximately 50 nm is formed by a PVD method.

After that, as shown in FIG. 3S, the silicon oxide film 28 is formed onthe barrier film 27. As the silicon oxide film 28, a NSG film is formedby a plasma CVD method in which source gas is TEOS, for example.Besides, a thickness of the silicon oxide film 28 is, for example,approximately 2600 nm. Subsequently, plasma annealing is performed withN₂O plasma in a CVD apparatus, for example, and thereby, a surface ofthe silicon oxide film 28 is nitride. The plasma annealing is performedat 350° C. for 4 minutes, for example. In the plasma annealing,dehydration treatment of the silicon oxide film 28 is also performed.

Next, the silicon oxide film 29 is formed on the silicon oxide film 28.As the silicon oxide film 29, a NSG film is formed by a plasma CVDmethod in which source gas is TEOS, for example. Besides, a thickness ofthe silicon oxide film 29 is, for example, approximately 100 nm. Next,plasma annealing is performed with N₂O plasma in a CVD apparatus, forexample, and thereby, the surface of the silicon oxide film 29 isnitride. The plasma annealing is performed at 350° C. for 2 minutes, forexample. In the plasma annealing, dehydration treatment of the siliconoxide film 29 is also performed.

After that, as shown in FIG. 3T, the silicon oxide film 29, the siliconoxide film 28, the barrier film 27 and the barrier film 25 are patternedwith a resist mask (not shown) in which a predetermined pattern isformed, and thereby, the contact holes 30 reaching the wirings 24 a areformed.

Subsequently, a TiN film with a thickness of approximately 50 nm isformed as a barrier metal film (not shown) by a PVD method, for example,for the whole surface. Next, a tungsten film with a thickness ofapproximately 650 nm is formed by a CVD method, for example, for thewhole surface. Next, the tungsten film and the TiN film are polished bya CMP method, for example, until the silicon oxide film 29 is exposed.As a result of this, the tungsten film remains in the contact hole 30,and the conductive plugs 31 are composed of this tungsten film as shownin FIG. 3U. After that, a conductive film 32 is formed by a PVD method,for example. When the conductive film 32 is formed, for example, an AlCualloy film with a thickness of 550 nm, a Ti film with a thickness of 5nm and a TiN film with a thickness of 150 nm are sequentially formed.

Subsequently, as shown in FIG. 3V, the conductive film 32 is patternedwith a resist mask (not shown) in which a predetermined pattern isformed, and thereby, the wirings 32 a are formed. Next, the siliconoxide film 33 covering the wirings 32 a is formed. As the silicon oxidefilm 33, a NSG film is formed by a plasma CVD method in which source gasis TEOS, for example. Besides, a thickness of the silicon oxide film 33is, for example, approximately 2200 nm. Next, the surface of the siliconoxide film 33 is polished by a CMP method, for example, and thereby, itis flattened. After that, plasma annealing is performed with N₂O plasmain a CVD apparatus, for example, and thereby, the surface of the siliconoxide film 33 is nitride. The plasma annealing is performed at 350° C.for 4 minutes, for example.

Subsequently, the silicon oxide film 34 with a thickness of, forexample, approximately 100 nm is formed on the silicon oxide film 33. Asthe silicon oxide film 34, a NSG film is formed by a plasma CVD methodin which source gas is TEOS, for example. Next, plasma annealing isperformed with N₂O plasma in a CVD apparatus, for example, and thereby,a surface of the silicon oxide film 34 is nitride. The plasma annealingis performed at 350° C. for 2 minutes, for example.

Next, as shown in FIG. 3W, the silicon oxide films 34 and 33 arepatterned with a resist mask (not shown) in which a predeterminedpattern is formed, and thereby, the contact holes 35 reaching thewirings 32 a are formed. After that, the TiN film with a thickness ofapproximately 50 nm is formed as a barrier metal film (not shown) forthe whole surface by a PVD method, for example. Subsequently, a tungstenfilm with a thickness of approximately 650 nm is formed for the wholesurface by a CVD method, for example. Next, the tungsten film and theTiN film are polished by a CMP method, for example, until the siliconoxide film 34 is exposed. As a result of this, the tungsten films remainin the contact holes 35, and the conductive plugs 36 are composed ofthese tungsten films. Subsequently, the wirings 37 are formed by a PVDmethod, for example. When the wirings 37 are formed, for example, anAlCu alloy film with a thickness of 500 nm and a TiN film with athickness of 150 nm are sequentially formed, and these films arepatterned.

After that, as shown in FIG. 3X, the silicon oxide film 38 covering thewirings 37 is formed. As the silicon oxide film 38, a NSG film is formedby a plasma CVD method in which source gas is TEOS, for example. Athickness of the silicon oxide film 38 is, for example, approximately100 nm. Subsequently, plasma annealing is performed with N₂O plasma in aCVD apparatus, for example, and thereby, a surface of the silicon oxidefilm 38 is nitride. The plasma annealing is performed at 350° C. for 2minutes, for example.

Next, the silicon nitride film 39 with a thickness of approximately 350nm is formed on the silicon oxide film 38 by a plasma CVD method, forexample. The silicon oxide film 38 and the silicon nitride film 39function as a passivation film.

Next, as shown in FIG. 3Y, the silicon nitride film 39 and the siliconoxide film 38 are patterned with a resist mask (not shown) in which apredetermined pattern is formed, and thereby, the opening 40 exposing apart of the wirings 37 is formed in the pad portion 104. Incidentally,in this patterning, the TiN film constituting the wirings 37 is alsoremoved.

After that, a photosensitive polyimide is coated, and thereby, aprotective film 41 with a thickness of approximately 3 μm is formed onthe silicon nitride film 39. Subsequently, an exposure and a developmentare performed for the protective film 41, and thereby, the opening 42exposing the opening 40 is formed in the pad portion 104.

Heat treatment is performed at 310° C. for 40 minutes in a horizontalfurnace, for example. During the heat treatment, nitride is suppliedwith the flow rate of 100 liter/minute, for example. As a result, theprotective film 41 composed of the photosensitive polyimide is cured.

As stated above, in the reference example, the barrier film 1062 existsover the silicon oxide films 1060 and 1061, and leaving of moisture inthe silicon oxide films 1060 and 1061 for upward is disturbed by thebarrier film 1062, as shown in FIG. 5B. Accordingly, the moisture isleaving via the contact hole 1068, and the formations of the barriermetal film and the tungsten film are disturbed.

On the contrary, in the first embodiment, nothing exists to disturbleaving of moisture over the silicon oxide films 28 and 29 after thecontact hole 30 is formed, as shown in FIG. 5A. Accordingly, almost allof the moisture in the silicon oxide films 28 and 29 leaving from thesurface of the silicon oxide film 29 for outside when it is heatedduring the formation processes of the barrier metal film and thetungsten film. Namely, the moisture leaving via the contact holes 30 isextremely little. Consequently, the fine barrier metal film and tungstenfilm are formed, and the properties become stable.

Second Embodiment

Next, a second embodiment is described. FIG. 6A to FIG. 6B are sectionalviews showing a manufacturing method of a ferroelectric memory(semiconductor device) according to the second embodiment in processsequence.

In manufacturing the ferroelectric memory according to the secondembodiment, first, the processes until forming the silicon oxide film 26are performed as same as the first embodiment, as shown in FIG. 3P.

Next, as shown in FIG. 6A, the silicon oxide film 26 and the barrierfilm 25 are polished until the surfaces of the wirings 24 a are exposedby a CMP method, for example. After that, plasma annealing with N₂Oplasma is performed in a CVD apparatus, for example, and thereby, thesurface of the silicon oxide film 26 is nitride. The plasma annealing isperformed at 350° C. for 4 minutes, for example. In this plasmaannealing, dehydration treatment of the silicon oxide film 26 is alsoperformed.

Next, as shown in FIG. 6B, the barrier film 27 is formed on the wirings24 a, the barrier film 25 and the silicon oxide film 26. As the barrierfilm 27, an aluminum oxide film with a thickness of, for example,approximately 50 nm is formed by a PVD method.

After that, the processes from forming the silicon oxide film 28 areperformed as same as the first embodiment.

According to the second embodiment as described above, as shown in FIG.7, the similar structure to the first embodiment can be obtained exceptthat the barrier film 27 is directly in contact with the surface of thewirings 24 a without being intervened by the barrier film 25.

Consequently, it is possible that the moisture leaves from the surfaceof the silicon oxide film 29 after the formation of the contact holes 30as same as the first embodiment. Accordingly, the effect similar to thefirst embodiment can be obtained.

Third Embodiment

Next, a third embodiment is described. FIG. 8 is a sectional viewshowing a ferroelectric memory (semiconductor device) according to thethird embodiment.

In the present embodiment, a silicon oxide film 61 is formed between theadjacent wirings 32 a. A barrier film 62 is formed on the silicon oxidefilm 61 and the wirings 32 a. A silicon oxide film 63 is formed on thebarrier film 62. Namely, the silicon oxide film 61, the barrier film 62and the silicon oxide film 63 are formed instead of the silicon oxidefilm 33 in the first embodiment.

In manufacturing the ferroelectric memory according to the thirdembodiment as described above, first, the processes until forming thewirings 32 a are performed as same as the first embodiment. Next, thesilicon oxide film 61 covering the wirings 32 a is formed, and it isflattened by a CMP method, for example, until the wirings 32 a areexposed. As the silicon oxide film 61, a NSG film is formed by a plasmaCVD method in which source gas is TEOS for example. After that, plasmaannealing is performed with N₂O plasma in a CVD apparatus, for example,and thereby, a surface of the silicon oxide film 61 is nitride. Next,the barrier film 62 is formed on the silicon oxide film 61 and thewirings 32 a. As the barrier film 62, an aluminum oxide film is formedby a PVD method, for example. Subsequently, the silicon oxide film 63 isformed on the barrier film 62, and it is flattened. As the silicon oxidefilm 63, a NSG film is formed by a plasma CVD method in which source gasis TEOS, for example. After that, plasma annealing is performed with N₂Oplasma in a CVD apparatus, for example, and thereby, a surface of thesilicon oxide film 63 is nitride.

The processes from forming the silicon oxide film 34 are then performedas same as the first embodiment.

In the third embodiment as described above, the flat barrier film 62 isadded, and therefore, it is possible to prevent the penetration ofmoisture more surely compared to the first embodiment. Besides, thebarrier film 62 is in contact with the surfaces of the wirings 32 a, andtherefore, when the conductive plugs 36 are formed, it is possible thatthe moisture in the silicon oxide films 63 and 34 leaves from thesurface of the silicon oxide film 34. Consequently, the formation of theconductive plugs 36 is not disturbed.

Fourth Embodiment

Next, a fourth embodiment is described. FIG. 9 is a sectional viewshowing a ferroelectric memory (semiconductor device) according to thefourth embodiment.

In the fourth embodiment, the silicon oxide film 61, the barrier film 62and the silicon oxide film 63 are formed instead of the silicon oxidefilm 33 in the second embodiment. Consequently, the effect of the thirdembodiment together with the effect of the second embodiment can beobtained.

Incidentally, in the present embodiment, the barrier film is not limitedto the aluminum oxide film, but it may be a film capable of preventingthe diffusion of at least hydrogen or moisture, such as a metal oxidefilm or a metal nitride film. For example, a titanium oxide film, an Alnitride film, an Al oxynitride film, a Ta oxide film, a Ta nitride filmand a Zr oxide film, a Si oxynitride film and the like may be used. Themetal oxide film is minute, and therefore, it is possible to surelyprevent the diffusion of hydrogen even if the film is relatively thin.Consequently, it is preferable that the metal oxide is used as thebarrier film from a view of miniaturization.

Besides, a crystal structure of substances composing the ferroelectricfilm is not limited to the perovskite type structure, but it may be, forexample, a Bi-layer structure. Besides, a composition of substancescomposing the ferroelectric film is not limited in particular. Forexample, Pb (lead), Sr (strontium), Ca (calcium), Bi (bismuth), Ba(barium), Li (lithium) and/or Y (yttrium) may be contained as anacceptor element, and Ti (titanium), Zr (zirconium), Hf (hafnium), V(vanadium), Ta (tantalum), W (tungsten), Mn (manganese), Al (aluminum),Bi (bismuth) and/or Sr (strontium) may be contained as a donor element.

For example, Pb(Zr, Ti)O₃, (Pb, Ca)(Zr, Ti)O₃, (Pb, Ca) (Zr, Ti, Ta)O₃,(Pb, Ca) (Zr, Ti, W)O₃, (Pb, Sr) (Zr, Ti)O₃, (Pb, Sr) (Zr, Ti, W)O₃,(Pb, Sr)(Zr, Ti, Ta)O₃, (Pb, Ca, Sr)(Zr, Ti)O₃, (Pb, Ca, Sr)(Zr, Ti,W)O₃, (Pb, Ca, Sr) (Zr, Ti, Ta)O₃, SrBi₂ (Ta_(X)Nb_(1-X))₂O₉,SrBi₂Ta₂O₉, Bi₄Ti₂O₁₂, Bi₄Ti₃O₉, and BaBi₂Ta₂O₉ are cited as a chemicalformula of the substances composing the ferroelectric film, but it isnot limited to the above. Besides, Si may be added to the above.

Besides, the present embodiment is not limited to be applied to theferroelectric memory, but it may be applied to, for example, a DRAM andso on. When it is applied to the DRAM, a high dielectric constant film,for example, such as a (BaSr)TiO₃ film (BST film), an SrTiO₃ film (STOfilm), a Ta₂O₅ film may be used instead of the ferroelectric film.Incidentally, the high dielectric constant film means a dielectricconstant film of which relative dielectric constant is higher than asilicon dioxide.

Besides, compositions of the top electrode and the bottom electrode arenot limited in particular. The bottom electrode may be composed of, forexample, Pt (platinum), Ir (iridium), Ru (ruthenium), Rh (rhodium), Re(rhenium), Os (osmium) and/or Pd (palladium), or it may be composed ofan oxide of the above. Layers lower than a noble metal cap film of thetop electrode may be composed of, for example, the oxide of Pt, Ir, Ru,Rh, Re, Os and/or Pd. Besides, the top electrode may be constituted bystacking plural films.

Further, a structure of the ferroelectric memory cell is not limited tothe 1T1C-type, but it may be a 2T2C-type. Besides, the ferroelectricmemory may have a constitution in which the ferroelectric capacitor initself is used as both a storage portion and a switching portion. Inthis case, the structure may become the one in which the ferroelectriccapacitor is formed instead of a gate electrode of a MOS transistor.Namely, the ferroelectric capacitor is formed on a semiconductorsubstrate via a gate insulating film.

Besides, a forming method of the ferroelectric film is not limited inparticular. For example, a sol-gel method, a metallo-organicdecomposition (MOD) method, a CSD (Chemical Solution Deposition) method,a chemical vapor deposition (CVD) method, an epitaxial growth method, asputtering method, a MOCVD (Metal Organic Chemical Vapor Deposition)method, and the like may be adopted.

Besides, in the above-stated embodiments, a structure of theferroelectric capacitor is a planar structure, but a ferroelectriccapacitor having a stack structure may be used.

INDUSTRIAL APPLICABILITY

As stated above, according to the present embodiment, a barrier layer ofwhich surface is flat is formed, and therefore, a high barrier propertycan be obtained. Besides, since the barrier layer directly covers firstwirings, this barrier layer does not disturb leaving of moisture in aninterlayer insulating film positioning between second wirings and thefirst wirings. Consequently, it is possible to keep an electricalconnection between the first wirings and the second wirings in a goodstate. Further, in a case where a barrier film (a third barrier film) isprovided on the second wirings, even if some defects occur at both ofthe barrier layer and the barrier film, defected positions may bedisplaced from one another in most cases. Accordingly, it is possible toprevent penetration of hydrogen and moisture by at least one of them.Namely, it is possible to secure the barrier property more surely.

1. A semiconductor device, comprising: a ferroelectric capacitor above asemiconductor substrate, and including a bottom electrode, aferroelectric film and a top electrode; a first wiring above saidferroelectric capacitor, a part of said first wiring being connected toone of said top electrode and bottom electrode; a barrier layer directlycovering said first wiring, and preventing diffusion of hydrogen ormoisture, a surface of said barrier layer being flat; an interlayerinsulating film on said barrier layer; and a second wiring on saidinterlayer insulating film, a part of said second wiring being connectedto said first wiring.
 2. The semiconductor device according to claim 1,wherein said barrier layer includes: a first barrier film covering aside surface and an upper surface of said first wiring; and a flatsecond barrier film on said first barrier film.
 3. The semiconductordevice according to claim 1, wherein said barrier layer includes: afirst barrier film covering a side surface of said first wiring; and aflat second barrier film covering a upper surface of said first wiring.4. The semiconductor device according to claim 1, wherein a filmpreventing diffusion of hydrogen or moisture does not exist between saidbarrier layer and said second wiring.
 5. The semiconductor deviceaccording to claim 1, further comprising a third barrier film directlycovering said second wiring, and preventing diffusion of hydrogen ormoisture, a surface of said third barrier film is flat.
 6. Thesemiconductor device according to claim 2, wherein said first and secondbarrier films respectively are metal oxide films.
 7. The semiconductordevice according to claim 3, wherein said first and second barrier filmsrespectively are metal oxide films.
 8. The semiconductor deviceaccording to claim 2, wherein said first and second barrier filmsrespectively are aluminum oxide films or titanium oxide films.
 9. Thesemiconductor device according to claim 3, wherein said first and secondbarrier films respectively are aluminum oxide films.
 10. A manufacturingmethod of a semiconductor device, comprising the steps of: forming aferroelectric capacitor including a bottom electrode, a ferroelectricfilm and a top electrode above a semiconductor substrate; forming afirst wiring, a part of which is connected to one of the top electrodeand the bottom electrode, above the ferroelectric capacitor; forming abarrier layer, a surface of which is flat, directly covering the firstwiring, and preventing diffusion of hydrogen or moisture; forming aninterlayer insulating film on the barrier layer; and forming a secondwiring, a part of which is connected to the first wiring, on theinterlayer insulating film.
 11. The manufacturing method of asemiconductor device according to claim 10, wherein said step of formingthe barrier layer includes the steps of: forming a first barrier filmcovering a side surface and an upper surface of the first wiring; andforming a flat second barrier film on the first barrier film.
 12. Themanufacturing method of a semiconductor device according to claim 11,further comprising the steps of, between said step of forming the firstbarrier film and said step of forming the second barrier film: formingan insulating film on the first barrier film; and flattening theinsulating film until an upper surface of the first barrier film isexposed.
 13. The manufacturing method of a semiconductor deviceaccording to claim 10, wherein said step of forming the barrier layerincludes the steps of: forming a first barrier film covering a sidesurface of the first wiring; and forming a flat second barrier filmcovering an upper surfaces of the first wiring.
 14. The manufacturingmethod of a semiconductor device according to claim 13, wherein saidstep of forming the first barrier film includes the steps of: forming amaterial film of the first barrier film covering the side surface andthe upper surface of the first wiring; forming an insulating film on thematerial film; and flattening the insulating film and the material filmuntil the upper surface of the first wiring are exposed.
 15. Themanufacturing method of a semiconductor device according to claim 10,further comprising the steps of, between said step of forming theinterlayer insulating film and said step of forming the second wiring:forming a contact hole reaching the first wiring in the interlayerinsulating film and the barrier layer; and forming a conductive pluginside the contact hole.
 16. The manufacturing method of a semiconductordevice according to claim 10, wherein a film preventing the diffusion ofhydrogen or moisture is not formed between said step of forming thebarrier layer and said step of forming the second wiring.
 17. Themanufacturing method of a semiconductor device according to claim 10,further comprising the step of, after said step of forming the secondwiring, forming a third barrier film, a surface of which is flat,directly covering the second wiring, and preventing the diffusion ofhydrogen or moisture.
 18. The manufacturing method of a semiconductordevice according to claim 11, wherein metal oxide films are formed asthe first and second barrier films respectively.
 19. The manufacturingmethod of a semiconductor device according to claim 13, wherein metaloxide films are formed as the first and second barrier filmsrespectively.